Purpose: Wireless Sensor Networks (WSNs) are foundational to modern Internet of Things (IoT) applications, but they face a critical challenge: a fundamental trade-off between energy efficiency and security. While many routing protocols exist, they often fail to address both aspects concurrently, leaving networks vulnerable to common attacks such as blackhole, flooding, spoofing, and wormhole attacks while draining limited power resources. This paper introduces a novel, secure opportunistic routing protocol designed to holistically address this dual-objective problem.

Methodology: The proposed protocol employs a new system architecture that incorporates Associate Cluster Heads (ACHs) to create resilient routing paths. It utilizes a multi-layered security approach, including a neighbor validation mechanism to prevent spoofing and a request-thresholding mechanism to effectively mitigate flooding attacks. A novel dynamic trust management model is also integrated to quantify node trustworthiness and provide cluster-wide reputation management. The performance of the protocol was evaluated through extensive simulations, measuring key metrics such as packet delivery ratio, energy consumption, and network lifetime against established WSN routing methods.

Results: The simulation results demonstrate that the proposed scheme significantly enhances network performance. It achieved a higher packet delivery ratio, confirming its effectiveness in ensuring reliable data transmission even under adversarial conditions. Furthermore, the protocol exhibited substantial improvements in energy efficiency, leading to an extended network lifetime compared to traditional and other state-of-the-art routing techniques. The integrated security mechanisms proved successful in identifying and neutralizing various attacks, with performance remaining high even when the percentage of malicious nodes increased.

Conclusion: The findings confirm that the proposed secure opportunistic routing protocol provides a robust and practical solution for WSNs. By effectively balancing the critical trade-off between energy optimization and security, the model not only improves resilience against a range of attacks but also extends the operational lifespan of the network. This research presents a significant step toward developing more secure and sustainable WSN and IoT deployments for real-world applications.